Announcements

A python port of Announcements from Pharo Smalltalk

Overview

Announcements can be used to announce Events such as a button click or a state change. It encodes events as classes (each event is represented by an Announcement subclass.) Subscriptors to an announcement can be any callable. Subscriptors can accept zero arguments (we call those “actions”) one argument (an instance of the Announcement is passed, you can use that instance to pass relevant information to the subscriber), or two arguments (the Announcement instance and the announcer are passed.) A dummy example that subscribes a list append method to an event. Some data is attached to the event instance:

>>> class Event(Announcement):
...     pass
>>> subscriber = []
>>> announcer = Announcer()
>>> announcer.subscribe(Event, send="append", to=subscriber)
>>> newevent = Event()
>>> newevent.usefullData = 42
>>> announcer.announce(newevent)

TODO

• Thread safety - Subscriptions must be added, removed or executed in a thread safe manner.
• Error handling - St version handles errors in another process by passing the exception to the enclosing context after fork’ing.
• Convenience - Many methods in the ST version are not yet implemented. We just did enough for passing the Announcements-Core tests.

Note

This is a toy for now, you should probably use Blinker instead: http://discorporate.us/projects/Blinker/.